refactor: split backend by context instead of type 'controllers/models/...'

app/admin/middlewares/is_admin_middleware.ts

@@ -0,0 +1,11 @@
+import type { HttpContext } from '@adonisjs/core/http';
+import type { NextFn } from '@adonisjs/core/types/http';
+
+export default class AdminMiddleware {
+	async handle(ctx: HttpContext, next: NextFn) {
+		if (!ctx.auth.user?.isAdmin) {
+			return ctx.response.redirectToNamedRoute('dashboard');
+		}
+		return next();
+	}
+}